For many off road type vehicles such as agricultural or industrial tractors, it is conventional to cool the oil which is used to lubricate the axle assembly. One method of cooling this oil is to recirculate the oil between the transmission case and the axle assembly such that the warm oil is able to intermix with a larger quantity of cooler oil before being returned to the axle assembly. In addition to maintaining a certain level within the axle assembly, it is normal to have a hydraulic actuator such as a differential clutch located within the axle assembly. When the clutch is engaged, the differential is locked up and both axles are driven as one and when the clutch is released, both axles can be driven independently. Such hydraulic actuators are susceptible to leaking fluid at various joints or seals during operation and this leaked oil can increase the oil level within the axle assembly. This presents a problem in that as the oil level increases, the efficiency of the axle decreases, greater cavitation can occur, and a larger quantity of oil is heated which can result in overheating of the axle assembly.
Various attempts to correct this problem have run the gamut of operating the axle assembly completely full of oil to using complex seals to prevent leakage. The first option is not feasible for any vehicle which requires a full speed range and the second option has proven costly as well as not being completely satisfactory.
Now a fluid level control system has been invented which solves the above-identified problems in an efficient and economical manner.